It has been known in the art to build packages for containing micro-electromechanical systems (“MEMS”) microphones. A typical package includes the MEMS transducer die, along with a separate complimentary metal-oxide-semiconductor (“CMOS”) die for amplification of the signal arising from the MEMS transducer die. These die are mounted onto a substrate in a side-by-side formation within a package and wire bonded to each other and the substrate. For an example of this type of configuration, one can reference U.S. Pat. Nos. 6,781,231 and 7,242,089, the disclosures of which are incorporated herein by reference (including materials used to construct such types of packages, MEMS dies, and CMOS dies; dimension ranges for all parts/components; mechanical and/or electrical coupling methods; and any related manufacturing details). FIG. 1 also provides an example of this configuration. A package 101 comprises a substrate 102 and a cover 103. The package 101 has a MEMS transducer die 104 and a CMOS die 106 attached to the substrate 102. Because of the location of an acoustic port 108 above the transducer 104, a diaphragm 105 of the transducer 104 divides the package 101 into a back volume 107 and a front volume 109 (adjacent to the acoustic port 108). It is desirable to reduce the footprint of packages, such as those described above, to better fit into a variety of consumer electronic devices, such as cell phones, music players, computing devices, etc.
To this end, attempts have been made to stack the dies of a given package to reduce the footprint of the package. See, for example, the package 201 of FIG. 2. In this configuration, a CMOS die 206 is placed at least partially under a MEMS die 204 to reduce the footprint of the package. A major drawback with placement of the CMOS die 206 underneath the MEMS die 204 is that by doing so, either the height of the package is increased or if the MEMS die 204 is thinned, the back volume 207 of the package is decreased, thereby negatively impacting the microphone sensitivity and signal to noise ratio. It is at least one objective of the present invention to address this drawback.